Generally, the present invention relates to a method and apparatus for detecting the distance between vehicles. More particularly the present invention relates to a method and apparatus for detecting vehicle distance based on reflected waves of a beam scanned by radar.
Recently, vehicle design trends have been moving from passive vehicle control, in which the behavior of a vehicle is controlled by a driver, to active control, in which a vehicle actively controls its own behavior. For example, an adaptive cruise control (ACC) system that controls a vehicle""s speed to automatically maintain a certain distance to a preceding vehicle has almost been commercialized.
In order to safely provide an ACC system there must be an accurate technique for detecting distance to a preceding vehicle. Traditionally, radar, using laser or millimeter waves has been widely adopted to detect the distance to a preceding vehicle. Using such a system to detect the distance, a radio wave (laser or millimeter wave) is projected to and reflected from a preceding vehicle. The reflected beam or wave is then detected and analyzed to calculate the distance to the preceding vehicle.
When the vehicles are running on a flat road, the distance to the preceding vehicle can be accurately measured. However, if the road undulates, the preceding vehicle may become positioned vertically higher or lower than the projected scanning radar beam from the vehicle equipped with an ACC. In such a case, the following vehicle may fail to detect the distance to the preceding vehicle. Therefore, a drawback of the existing device is that when the vertical undulation of the road is large a preceding vehicle falls outside the vertical width of the scanning beam. Therefore, no vehicle is detected and the vehicle distance detecting device would improperly judge the driving condition.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.
An exemplary apparatus for detecting distance to a preceding vehicle includes a radar for scanning a radar beam from the vehicle, a scanning angle adjusting for adjusting a scanning angle of the radar, a camera for acquiring a road image, and an electronic control unit. The electronic control unit is activated by predetermined software that comprises instructions for each step of a method for detecting distance to a preceding vehicle.
Another exemplary method for detecting distance to a preceding vehicle useful with the present invention includes receiving a signal of a road image from a camera and extracting lane markers from the road image. The method further includes adjusting a scanning angle of the radar based on the extracted lane markers and calculating a distance to the preceding vehicle using reflected waves of a radar beam scanned at the adjusted scanning angle.
In a further preferable embodiment, the scanning angle is adjusted by calculating a height within the image at which a horizontal distance between the extracted lane markers is a predetermined distance. Calculating the slope of the road from the calculated height and adjusting the scanning angle of the radar based on the calculated slope of the road.
In a still further preferable embodiment, the slope of a road is calculated based on a difference between the calculated height within the image at which a horizontal distance between the lane markers is a predetermined distance and a reference height at which a horizontal distance between lane markers is a predetermined distance.
In a still further preferable embodiment, the reference height within the image corresponding to lane markers separated by a predetermined horizontal distance is an average value of the calculated height within the image corresponding to lane markers separated by a predetermined horizontal distance over a predetermined period.